Oil recovery efficiency from subterranean reservoirs containing viscous hydrocarbons may be improved or enhanced with the injection of a chemical agent, such as solvent, surfactant, diluting liquid, detergent, wetting agent, emulsifier, foaming agent, or dispersant, into the reservoir. Enhanced oil recovery (EOR) techniques also include injection of heat energy, such as using steam or heated fluid, or injection of sound energy, such as using ultrasonic or supersonic waves. It has been recognized that sound waves or acoustic energy can be used to heat and reduce the viscosity of oil, increase the permeability of the reservoir formation, and generally induce migration of oil in the formation into the well bore.
For example, U.S. Pat. No. 6,279,653 to Wegener et al., dated Aug. 28, 2001, discloses an apparatus and process for producing heavy crude oil from a subterranean formation penetrated by a vertical well. In this process, an aqueous alkaline chemical solution is introduced into or formed in the well bore. The aqueous alkaline chemical solution mixes and reacts with produced heavy crude oil in the vertical well bore and ultrasonic waves are emitted into the mixture to form an emulsion.
EOR through horizontal wells presents unique challenges, as compared to recovery through vertical wells, but also presents opportunities for innovative techniques to achieve improved results or efficiency.